Power amplifier noise suppression using feedback

ABSTRACT

A power amplifier system can include a power amplifier that provides amplification to a radio frequency signal associated with a first frequency band and outputs an amplified radio frequency signal. An acoustic wave bandpass filter such as a surface acoustic wave or bulk acoustic wave bandpass filter is arranged in a feedback configuration with respect to the power amplifier. The filter can pass through a portion of the amplified radio frequency signal corresponding to a second frequency to provide negative feedback to the power amplifier, resulting in a reduction in an amount of gain from the power amplifier within the second frequency band.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications, if any, for which a foreign or domesticpriority claim is identified in the Application Data Sheet of thepresent application are hereby incorporated by reference under 37 CFR1.57.

BACKGROUND Field

Embodiments relate generally to power amplifier modules. Morespecifically, embodiments are directed to noise suppression for poweramplifier modules.

Description of the Related Technology

Power amplifiers are used in many electronic devices to convert lowpower signals to higher power signals. For example, in a mobile devicesuch as a mobile phone, a power amplifier may be used to amplified an RFsignal to drive an antenna of a transceiver for transmitting wirelessdata.

It can be desirable in power amplifier systems to reduce undesired noisein certain frequency bands.

SUMMARY

Electronic devices that transmit an RF signal on a desired frequencyband are typically required to minimize emissions into other “protected”frequency bands, for example the GPS band. Where such an electronicdevice includes a power amplifier, the unwanted emissions may be createdby amplification of unwanted RF power originating from various sourcesand reaching the power amplifier input. These sources include thermalnoise elevated by the noise figure of the power amplifier itself, noiseconducted directly from any preceding stages that drive the poweramplifier, and unwanted signals radiated or conducted from other systemsor modules within the electronic device. It is desirable to minimizeundesired emission in the protected band (e.g., GPS band) because it mayinterfere with and inhibit the operation associated with the protectedband (e.g., inhibit operation of GPS receivers).

In certain embodiments, the present disclosure relates to a poweramplifier system comprising a noise suppression feedback circuit. Thepresent disclosure also relates to a wireless device containing a poweramplifier system with a noise suppression feedback loop. The presentdisclosure also relates to a radio frequency module comprising asubstrate having a power amplifier system with a noise suppressionfeedback loop.

In some embodiments, a power amplifier system is provided. The poweramplifier system comprises a power amplifier configured to provideamplification to a radio frequency signal associated with a firstfrequency band and output an amplified radio frequency signal. The poweramplifier system further comprises a feedback loop. The feedback loopincludes a directional coupler configured to measure the amplified radiofrequency signal. The feedback loop further includes a surface acousticwave (SAW) bandpass filter configured to pass through a portion of theamplified radio frequency signal corresponding to a second frequencyband. An output of the SAW bandpass filter is coupled to an input of thepower amplifier to provide negative feedback to the power amplifier,such that an amount of gain from the power amplifier within the secondfrequency band is reduced.

In some embodiments, a power amplifier system is provided. The poweramplifier system comprises a power amplifier configured to provideamplification to a radio frequency signal associated with a firstfrequency band and output an amplified radio frequency signal. The poweramplifier system further comprises a feedback loop. The feedback loopcomprises a directional coupler configured to measure the amplifiedradio frequency signal. The feedback loop further comprises a bandpassfilter configured to pass through a portion of the amplified radiofrequency signal corresponding to a second frequency band. The feedbackloop further comprises a plurality of phase shifters comprising at leasta first phase shifter coupled between the directional coupler and aninput of the bandpass filter and a second phase shifter coupled to anoutput of the bandpass filter. A phase-shifted output of the bandpassfilter provides negative feedback to the power amplifier, such that anamount of gain from the power amplifier within the second frequency bandis reduced.

According to some aspects, the disclosure includes a power amplifiersystem comprising a power amplifier configured to provide amplificationto a radio frequency signal associated with a first frequency band andoutput an amplified radio frequency signal. The system can furthercomprise an acoustic wave bandpass filter arranged in a feedbackconfiguration with respect to the power amplifier. The acoustic wavebandpass filter can be configured to pass through a portion of theamplified radio frequency signal corresponding to a second frequencyband to an input of the power amplifier to provide negative feedback tothe power amplifier, resulting in a reduction in an amount of gain fromthe power amplifier within the second frequency band.

The first frequency band can correspond to a Long-Term Evolutionmid-band frequency band. The acoustic wave bandpass filter can be asurface acoustic wave filter or a bulk acoustic wave filter. The secondfrequency band can correspond to a global positioning system frequencyband.

The system can comprise a directional coupler positioned between anoutput of the power amplifier and an input of the acoustic wave bandpassfilter. The system can comprise at least one phase shifter coupledbetween an output of the power amplifier and an input of the acousticwave bandpass filter. The system can according to some embodimentscomprise at least one phase shifter coupled between the output of theacoustic wave bandpass filter and an input of the power amplifier.

According to additional aspects, a wireless device comprises atransceiver configured to generate a radio frequency signal associatedwith a first frequency band. The device can also include a poweramplifier configured to provide amplification to the radio frequencysignal and output an amplified radio frequency signal. An acoustic wavebandpass filter can be arranged in a feedback configuration with respectto the power amplifier. The acoustic wave bandpass filter can beconfigured to pass through a portion of the amplified radio frequencysignal corresponding to a second frequency band to an input of the poweramplifier to provide negative feedback to the power amplifier, resultingin a reduction in an amount of gain from the power amplifier within thesecond frequency band.

The first frequency band can correspond to a Long-Term Evolutionmid-band frequency band. The acoustic wave bandpass filter can a surfaceacoustic wave filter or a bulk acoustic wave filter. The the secondfrequency band can correspond to a GPS frequency band.

The device can further include a directional coupler positioned betweenan output of the power amplifier and an input of the acoustic wavebandpass filter.

At least one phase shifter can be coupled between an output of the poweramplifier and an input of the acoustic wave bandpass filter. At leastone phase shifter can be coupled between the output of the acoustic wavebandpass filter and an input of the power amplifier.

A packaged module according to yet further aspects comprises a packagesubstrate and a power amplifier supported by the package substrate andconfigured to provide amplification to the radio frequency signal andoutput an amplified radio frequency signal. The module can furthercomprise an acoustic wave bandpass filter arranged in a feedbackconfiguration with respect to the power amplifier, the acoustic wavebandpass filter configured to pass through a portion of the amplifiedradio frequency signal corresponding to a second frequency band to aninput of the power amplifier to provide negative feedback to the poweramplifier. This can result in a reduction in an amount of gain from thepower amplifier within the second frequency band.

The first frequency band can correspond to a Long-Term Evolutionmid-band frequency band. The second frequency band can correspond to aglobal positioning system frequency band.

The the acoustic wave bandpass filter can be a surface acoustic wavefilter or a bulk acoustic wave filter.

The packaged module can further comprise a directional couplerpositioned between an output of the power amplifier and an input of theacoustic wave bandpass filter. At least one phase shifter can be coupledbetween an output of the power amplifier and an input of the acousticwave bandpass filter. At least one phase shifter can be coupled betweenthe output of the acoustic wave bandpass filter and an input of thepower amplifier.

A power amplifier system according to further aspects of the disclosurecomprises a power amplifier configured to provide amplification to aradio frequency signal associated with a first frequency band and tooutput an amplified radio frequency signal. The system can comprise abandpass filter arranged in a feedback loop with respect to the poweramplifier and configured to pass through a portion of the amplifiedradio frequency signal corresponding to a second frequency band. A firstphase shifter can be positioned in the feedback loop, an output of thefeedback loop providing negative feedback to an input of the poweramplifier.

The first phase shifter can be positioned between an output of the poweramplifier and an input of the bandpass filter. A second phase shiftercan be positioned between an output of the bandpass filter and the inputto the power amplifier. The first phase shifter can be positionedbetween an output of the bandpass filter and the input to the poweramplifier. A directional coupler can be included, and positioned betweenan output of the power amplifier and an input of the bandpass filter.

The bandpass filter may be a surface acoustic wave filter or a bulkacoustic wave filter.

The first frequency band can correspond to a Long-Term Evolutionmid-band frequency band. The second frequency band can correspond toundesired noise. The second frequency band can correspond to a globalpositioning system frequency band.

According to additional aspects, a packaged module comprises a packagesubstrate and a power amplifier supported by the package substrate, thepower amplifier configured to provide amplification to a radio frequencysignal associated with a first frequency band and output an amplifiedradio frequency signal. The module can further include a bandpass filterarranged in a feedback loop with respect to the power amplifier andconfigured to pass through a portion of the amplified radio frequencysignal corresponding to a second frequency band. The module can alsohave a first phase shifter positioned in the feedback loop, an output ofthe feedback loop providing negative feedback to an input of the poweramplifier.

The first phase shifter can be positioned between an output of the poweramplifier and an input of the bandpass filter. A second phase shiftercan be positioned between an output of the bandpass filter and the inputto the power amplifier. The first phase shifter can be positionedbetween an output of the bandpass filter and the input to the poweramplifier. A directional coupler can be positioned between an output ofthe power amplifier and an input of the bandpass filter.

The bandpass filter can be a surface acoustic wave filter or a bulkacoustic wave filter.

The first frequency band can correspond to a Long-Term Evolutionmid-band frequency band. The second frequency band can correspond toundesired noise. The second frequency band can correspond to a globalpositioning system frequency band.

According to additional aspects a wireless device comprises atransceiver configured to generate a radio frequency signal associatedwith a first frequency band and a power amplifier configured to provideamplification to the radio frequency signal and output an amplifiedradio frequency signal. The device can also include a bandpass filterarranged in a feedback loop with respect to the power amplifier andconfigured to pass through a portion of the amplified radio frequencysignal corresponding to a second frequency band. A first phase shiftercan be positioned in the feedback loop, an output of the feedback loopproviding negative feedback to an input of the power amplifier.

The first phase shifter can be positioned between an output of the poweramplifier and an input of the bandpass filter. A second phase shiftercan be positioned between an output of the bandpass filter and the inputto the power amplifier. The first phase shifter can be positionedbetween an output of the bandpass filter and the input to the poweramplifier. A directional coupler can be positioned between an output ofthe power amplifier and an input of the bandpass filter.

The bandpass filter can be a surface acoustic wave filter or a bulkacoustic wave filter.

The first frequency band can correspond to a Long-Term Evolutionmid-band frequency band. The second frequency band can correspond toundesired noise. The second frequency band can correspond to a globalpositioning system frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a power amplifier module foramplifying a radio frequency (RF) signal.

FIG. 1B is a schematic diagram of a portion of a power amplifier modulefor amplifying RF signals, while suppressing noise associated with theGPS frequency band using a band reject filter, in accordance with someembodiments.

FIG. 2 is a schematic diagram of an example wireless device.

FIG. 3 is a schematic diagram of one embodiment of a power amplifiersystem.

FIGS. 4A to 4D are schematic diagrams of power amplifier feedbackcircuits, in accordance with some embodiments.

FIG. 5 is a graph showing a plot of the frequency response of the powergain of a power amplifier feedback system, in accordance with someembodiments.

FIG. 6 is a flowchart of a process for using feedback to suppress noisein a PA feedback system, in accordance with some embodiments.

DETAILED DESCRIPTION

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Power amplifiers are used in many electronic devices to convert lowpower signals (e.g., low power radio frequency, or RF, signals) tohigher power signals. For example, in a mobile device such as a mobilephone, one or more power amplifiers may be used to drive an antenna of atransceiver for transmitting wireless data.

FIG. 1A is a schematic diagram of a power amplifier module (PAM) 10 foramplifying an RF signal. The illustrated power amplifier module 10amplifies an RF signal (RF_IN) to generate an amplified RF signal(RF_OUT). In some embodiments, the amplified RF signal may be used todrive an antenna. The power amplifier module 10 can include one or morepower amplifier circuits implemented using one or more features of thepresent disclosure.

In some embodiments, a power amplifier module may, in addition toamplifying a desired lower power signal, also amplify an undesired noisesignal. Many electronic devices that transmit an RF signal on a desiredfrequency band are typically required to minimize emissions into other“protected” frequency bands, for example the GPS band. Where such anelectronic device includes a power amplifier, the unwanted emissions maybe created by amplification of unwanted RF power originating fromvarious sources and reaching the power amplifier input. These sourcesinclude thermal noise elevated by the noise figure of the poweramplifier itself, noise conducted directly from any preceding stagesthat drive the power amplifier, and unwanted signals radiated orconducted from other systems or modules within the electronic device. Assuch, the amplified RF signal may contain undesired noise in a frequencyband corresponding to the GPS system. It is desirable to minimize thisundesired emission in the protected band (e.g., GPS band) because it mayinterfere with and inhibit the operation of nearby receivers operatingin the protected band (e.g., GPS receivers).

In some embodiments, the PAM 10 may be configured to suppress noisepower from certain frequency bands (e.g., frequency bands associatedwith other systems/modules). For example, in some embodiments, the PAM10 may be part of a Long-Term Evolution (LTE) system such as an LTE MB(mid-band) system associated with an operating frequency that is closeto the frequency band of a GPS system. As such, the LTE MB PA module mayneed to be able to suppress noise associated with the GPS frequencyband.

FIG. 1B is a schematic diagram of a portion of the PAM 10 for amplifyingRF signals, while suppressing noise associated with the GPS frequencyband, in accordance with some embodiments. The PAM 10 may comprise apower amplifier circuit 102 that receives an input RF signal (e.g.,RF_IN). In addition, the PAM 10 comprises a band rejection filter 104.The band rejection filter 104 may be configured to suppress signalswithin a certain frequency band (e.g., a frequency band corresponding toGPS band noise). In some embodiments, the band rejection filter 104 maybe implemented as a surface acoustic wave (SAW) filter or a bulkacoustic wave (BAW) filter. It is understood that SAW or BAW bandrejection filters may be implemented as a hybrid of LC elements(inductors, capacitors) and SAW/BAW resonators.

The power amplifier 102 amplifies the input RF signal to produce anoutput signal. The output signal may contain undesired noise (e.g., GPSnoise) that has been amplified by the power amplifier 102. The outputsignal of the power amplifier 102 is passed through the band rejectionfilter 104 to form a filtered amplified signal (e.g., RF_OUT). Becausethe band reject filter 104 may be configured to filter or suppresssignals within a frequency band associated with the undesired noise, thepresence of undesired noise within the resulting amplified signal (e.g.,RF_OUT) may be minimized. SAW and/or BAW rejection filters such as thefilter 104 can be relatively costly, in part because they may bedesigned for handling relatively high power levels output by the poweramplifier 102. Further, the insertion loss of a SAW or BAW filter placeddirectly following the power amplifier causes a loss of power andtherefore a loss of power efficiency. Such loss may be of a magnitudefrom 1 dB up to several dB. For example a post-power-amplifier filterwith 3 dB insertion loss would dissipate half of the RF power emitted bythe power amplifier, in turn requiring a doubling of the output power ofthe power amplifier. Therefore it becomes desirable to provide a meansof reducing noise in a protected band without the use of apost-power-amplifier filter. Certain embodiments provided herein (e.g.,those shown in and described with respect to FIGS. 3 and 4A-6) addressthese and other challenges, and include power amplifier circuits havinga feedback arrangement for achieving reduction of undesired noise.

FIG. 2 is a schematic block diagram of an example wireless or mobiledevice 11. The wireless device 11 can include one or more poweramplifier modules implemented using one or more features of the presentdisclosure.

The example wireless device 11 depicted in FIG. 2 can represent amulti-band and/or multi-mode device such as a multi-band/multi-modemobile phone. By way of examples, Global System for Mobile (GSM)communication standard is a mode of digital cellular communication thatis utilized in many parts of the world. GSM mode mobile phones canoperate at one or more of four frequency bands: 850 MHz (approximately824-849 MHz for Tx, 869-894 MHz for Rx), 900 MHz (approximately 880-915MHz for Tx, 925-960 MHz for Rx), 1800 MHz (approximately 1710-1785 MHzfor Tx, 1805-1880 MHz for Rx), and 1900 MHz (approximately 1850-1910 MHzfor Tx, 1930-1990 MHz for Rx). Variations and/or regional/nationalimplementations of the GSM bands are also utilized in different parts ofthe world.

Code division multiple access (CDMA) is another standard that can beimplemented in mobile phone devices. In certain implementations, CDMAdevices can operate in one or more of 800 MHz, 900 MHz, 1800 MHz and1900 MHz bands, while certain W-CDMA and Long Term Evolution (LTE)devices can operate over, for example, 22 or more bands.

One or more features of the present disclosure can be implemented in theforegoing example modes and/or bands, and in other communicationstandards. For example, 802.11, 2G, 3G, 4G, LTE, and Advanced LTE arenon-limiting examples of such standards. To increase data rates, thewireless device 11 can operate using complex modulated signals, such as64 QAM signals.

In certain embodiments, the wireless device 11 can include switches 12,a transceiver 13, an antenna 14, power amplifiers 17 a, 17 b, a controlcomponent 18, a computer readable medium 19, a processor 20, a battery21, and a power management system 30. In some embodiments, the poweramplifiers 17 a, 17 b may be implemented as part of the PAM 10illustrated in FIG. 1A, and may correspond to the power amplifier 102illustrated in FIG. 1B.

The transceiver 13 can generate RF signals for transmission via theantenna 14. Furthermore, the transceiver 13 can receive incoming RFsignals from the antenna 14.

It will be understood that various functionalities associated with thetransmission and receiving of RF signals can be achieved by one or morecomponents that are collectively represented in FIG. 2 as thetransceiver 13. For example, a single component can be configured toprovide both transmitting and receiving functionalities. In anotherexample, transmitting and receiving functionalities can be provided byseparate components.

Similarly, it will be understood that various antenna functionalitiesassociated with the transmission and receiving of RF signals can beachieved by one or more components that are collectively represented inFIG. 2 as the antenna 14. For example, a single antenna can beconfigured to provide both transmitting and receiving functionalities.In another example, transmitting and receiving functionalities can beprovided by separate antennas. In yet another example, different bandsassociated with the wireless device 11 can operate using differentantennas or a single antenna.

In FIG. 2, one or more output signals from the transceiver 13 aredepicted as being provided to the antenna 14 via one or moretransmission paths 15. In the example shown, different transmissionpaths 15 can represent output paths associated with different bandsand/or different power outputs. For instance, the two example poweramplifiers 17 a, 17 b shown can represent amplifications associated withdifferent power output configurations (e.g., low power output and highpower output), and/or amplifications associated with different bands.Although FIG. 2 illustrates a configuration using two transmission paths15 and two power amplifiers 17 a, 17 b, the wireless device 11 can beadapted to include more or fewer transmission paths 15 and/or more orfewer power amplifiers.

In FIG. 2, one or more detected signals from the antenna 14 are depictedas being provided to the transceiver 13 via one or more receiving paths16. In the example shown, different receiving paths 16 can representpaths associated with different bands. For example, the four examplereceiving paths 16 shown can represent quad-band capability that somewireless devices are provided with. Although FIG. 2 illustrates aconfiguration using four receiving paths 16, the wireless device 11 canbe adapted to include more or fewer receiving paths 16.

To facilitate switching between receive and transmit paths, the switches12 can be configured to electrically connect the antenna 14 to aselected transmit or receive path. Thus, the switches 12 can provide anumber of switching functionalities associated with operation of thewireless device 11. In certain embodiments, the switches 12 can includea number of switches configured to provide functionalities associatedwith, for example, switching between different bands, switching betweendifferent power modes, switching between transmission and receivingmodes, or some combination thereof. The switches 12 can also beconfigured to provide additional functionality, including filteringand/or duplexing of signals.

FIG. 2 shows that in certain embodiments, a control component 18 can beprovided for controlling various control functionalities associated withoperations of the switches 12, the power amplifiers 17 a, 17 b, thepower management system 30, and/or other operating components.

In certain embodiments, a processor 20 can be configured to facilitateimplementation of various processes described herein. The processor 20can implement various computer program instructions. The processor 20can be a general purpose computer, special purpose computer, or otherprogrammable data processing apparatus.

In certain embodiments, these computer program instructions may also bestored in a computer-readable memory 19 that can direct the processor 20to operate in a particular manner, such that the instructions stored inthe computer-readable memory 19.

The illustrated wireless device 11 also includes the power managementsystem 30, which can be used to provide power amplifier supply voltagesto one or more of the power amplifiers 17 a, 17 b. For example, thepower management system 30 can be configured to change the supplyvoltages provided to the power amplifiers 17 a, 17 b to improveefficiency, such as power added efficiency (PAE). The power managementsystem 30 can be used to provide average power tracking (APT) and/orenvelope tracking (ET). In some embodiments, the power management system30 can include one or more LDO regulators used to generate poweramplifier supply voltages for one or more stages of the power amplifiers17 a, 17 b. In the illustrated implementation, the power managementsystem 30 is controlled using a power control signal generated by thetransceiver 13. In certain configurations, the power control signal isprovided by the transceiver 13 to the power management system 30 over aninterface, such as a serial peripheral interface (SPI) or MobileIndustry Processor Interface (MIPI). The wireless device 11 can includepower amplifier circuits having a feedback arrangement for reduction ofundesired noise, such as any of the circuits described herein. Forinstance, one or both of the power amplifiers 17 a, 17 b can be any ofthe power amplifier circuits shown in and described with respect toFIGS. 3 and 4A-6) below.

In certain configurations, the wireless device 11 may operate usingcarrier aggregation. Carrier aggregation can be used for both FrequencyDivision Duplexing (FDD) and Time Division Duplexing (TDD), and may beused to aggregate a plurality of carriers or channels, for instance upto five carriers. Carrier aggregation includes contiguous aggregation,in which contiguous carriers within the same operating frequency bandare aggregated. Carrier aggregation can also be non-contiguous, and caninclude carriers separated in frequency within a common band or indifferent bands.

Power Amplifier Feedback Circuit

As discussed above, in some embodiments, in order to suppress noise incertain (e.g., protected) frequency bands, a power amplifier 102 may becoupled to a band reject filter 104 configured to filter or suppressundesired signal in a protected frequency band. In some embodiments, thepower amplifier 102 coupled to the band reject filter 104 may correspondto the power amplifiers 17 a or 17 b illustrated in FIG. 2.

However, in some embodiments, because the band reject filter 104receives the direct output of the power amplifier 102, the band rejectfilter 104 may be required to have high power capacity and low loss atthe desired transmission frequency (e.g., the frequency band associatedwith LTE MB channel). Band reject filters meeting these requirements maybe uncommon or not commercial available.

In some embodiments, instead of using a band reject filter 104 directlycoupled to the output of a power amplifier 102, the PAM 10 may implementa band pass filter as part of a feedback loop for the power amplifier102, in order to suppress noise emission in a particular protected band(e.g., GPS band noise). This type of implementation in which noisereduction is achieved via a feedback arrangement may hereinafter bereferred to as a power amplifier feedback circuit (PA feedback circuit)or feedback-arranged PA circuit.

FIG. 3 is a schematic block diagram of one example of a system 26, whichcan include a portion of the wireless device 11 shown in FIG. 2. Theillustrated system 26 includes the switches 12, the antenna 14, adirectional coupler 24, a power management system 30, a power amplifierbias circuit 31, a feedback-arranged PA circuit 32, and a transceiver 33(which may correspond to the transceiver 13 as illustrated in FIG. 2).The illustrated transceiver 33 includes a baseband processor 34, atransmit digital-to-analog I/Q converter 40 which outputs a pair oftransmit I and Q lines to an I/Q modulator 37. The transceiver 33further includes a mixer 38, and a receive analog-to-digital I/Qconverter (ADC) 39, which outputs a pair of receive I and Q lines to thebaseband processor 34. Although not illustrated in FIG. 3 for clarity,the transceiver 33 can include circuitry associated with receivingsignals over one or more receive paths.

In some embodiments, the feedback-arranged PA circuit 32 may beimplemented as part of the PAM 10 illustrated in FIG. 1A. In someembodiments, the feedback-arranged PA 32 may comprise at least one poweramplifier (e.g., power amplifier 102, 17 a, and/or 17 b) and a feedbackloop having at least one band pass filter. Embodiments of thefeedback-arranged PA 32 are described in greater detail below withregards to FIGS. 4A-4D.

The baseband signal processor 34 can be used to generate an in-phase (I)signal and a quadrature-phase (Q) signal, which can be used to representa sinusoidal wave or signal of a desired amplitude, frequency, andphase. For example, the I signal can be used to represent an in-phasecomponent of the sinusoidal wave and the Q signal can be used torepresent a quadrature-phase component of the sinusoidal wave, which canbe an equivalent representation of the sinusoidal wave. In certainimplementations, the I and Q signals can be provided to the I/Qmodulator 37 in a digital format. The baseband processor 34 can be anysuitable processor configured to process a baseband signal. Forinstance, the baseband processor 34 can include a digital signalprocessor, a microprocessor, a programmable core, or any combinationthereof. Moreover, in some implementations, two or more basebandprocessors 34 can be included in the power amplifier system 26.

The I/Q modulator 37 can be configured to receive the I and Q signalsfrom the baseband processor 34 and to process the I and Q signals togenerate an RF signal. For example, the I/Q modulator 37 can includedigital-to-analog converters (DACs) configured to convert the I and Qsignals into an analog format, mixers for upconverting the I and Qsignals to RF, and a signal combiner for combining the upconverted I andQ signals into an RF signal suitable for amplification by thefeedback-arranged PA 32. In certain implementations, the I/Q modulator37 can include one or more filters configured to filter frequencycontent of signals processed therein.

The power amplifier bias circuit 31 receives a bias control signal fromthe transceiver 33, and generates one or more bias signals for thefeedback-arranged PA 32. In the illustrated configuration, the poweramplifier bias circuit 31 generates a first bias signal BIAS1 forbiasing a driver stage of the power amplifier 32 and a second biassignal BIAS2 for biasing an output stage of the power amplifier 32. Thebias signals BIAS1, BIAS2 can include current and/or voltage signals,and can be used, for example, to bias bases of bipolar transistorsand/or gates of field-effect transistors associated with the poweramplifier's stages. In certain configurations, the transceiver 33 cancontrol the bias signals generated by the power amplifier bias circuit31 to enhance the PAE of the power amplifier system 26. In oneembodiment, the transceiver 33 controls each of the first and secondbias signals BIAS1, BIAS2 to one of a multiple settings based on atleast one of a frequency band of operation or a power mode (for example,high power mode, medium power mode, or low power mode).

The feedback-arranged PA 32 can receive the RF signal from the I/Qmodulator 37 of the transceiver 33, and when enabled can provide anamplified RF signal to the antenna 14 via the switches 12. Thedirectional coupler 24 can be positioned between the output of thefeedback-arranged PA 32 and the input of the switches 12, and couplesthe signal output from the feedback arranged PA 32 to the transceiver 33(via the mixer 38 and ADC 39), thereby allowing an output powermeasurement of the power amplifier 32 that does not include insertionloss of the switches 12. However, other configurations of powermeasurement are possible.

In the illustrated configuration, the sensed output signal from thedirectional coupler 24 is provided to the mixer 38, which multiplies thesensed output signal by a reference signal of a controlled frequency.The mixer 38 operates to generate a downshifted signal by downshiftingthe sensed output signal's frequency content. The downshifted signal canbe provided to the ADC 39, which can convert the downshifted signal to adigital format suitable for processing by the baseband processor 34. Byincluding a feedback path between the output of the feedback-arranged PA32 and the baseband processor 34, the baseband processor 34 can beconfigured to dynamically adjust the I and Q signals to optimize theoperation of the power amplifier system 26. For example, configuring thepower amplifier system 26 in this manner can aid in controlling the PAEand/or linearity of the power amplifier 32. However, otherconfigurations of power control can be used. For example, mixer 38 andADC 39 could be replaced by a simple wideband power detector used forpower control only but not dynamic IQ signal adjustment.

The power management system 30 receives a power control signal from thetransceiver 33, and generates one or more power amplifier supplyvoltages for the feedback-arranged PA 32. In the illustratedconfiguration, the power management system 30 generates a first poweramplifier supply voltage V_(CC1) for powering a driver stage of thepower amplifier 32 and a second power amplifier supply voltage V_(CC2)for powering an output stage of the feedback-arranged PA 32. In certainconfigurations, the transceiver 33 can control the voltage levels of thepower amplifier supply voltages V_(CC1), V_(CC2) to enhance the poweramplifier system's PAE. Embodiments of the power management system 30are described in U.S. patent application Ser. No. 15/219,915, filed onJul. 26, 2016, which is hereby incorporated by reference in itsentirety.

FIG. 4A is a schematic diagram of a feedback-arranged PA 32 a, inaccordance with some embodiments. The feedback-arranged PA 32 a maycorrespond to the feedback-arranged PA 32 as illustrated in FIG. 3.

As illustrated in FIG. 4A, the feedback-arranged PA 32 a comprises thepower amplifier 102 configured to amplify an input signal (e.g., RF_IN)to produce an amplified output signal (e.g., RF_OUT). In addition,instead of using a band reject filter as illustrated in FIG. 1B, thefeedback-arranged PA 32 a comprises a feedback loop 402 configured toreduce an amount of noise from certain (e.g., protected) frequency bands(e.g., noise from GPS frequency bands). In some embodiments, thefeedback loop 402 comprises a directional coupler 404 coupled to theoutput of the power amplifier 102, and a band pass filter 406. Referringagain to FIG. 3, while in the illustrated configurations the coupler 24(FIG. 3) and the coupler 404 (FIGS. 4A-4D) are shown as two separatecouplers, in some embodiments the functions of the coupler 24 (FIG. 3)and the coupler 404 (FIGS. 4A-4D) performed by a single physical couplerwith its output split into two outputs as appropriate.

The input signal (e.g., RF_IN) amplified by the power amplifier 102 maybe associated with a particular frequency band. However, the poweramplifier 102 may also amplify noise from a certain (e.g., protected)frequency band (e.g., GPS frequency band), which may form a portion ofthe output of the power amplifier 102 (e.g., RF_OUT). The feedback loop402 may be configured to reduce an overall gain from the power amplifier102 at the protected frequency band, such that an amount of noise at theprotected frequency band in the output signal is reduced.

The directional coupler 404 may be similar to the directional coupler 24illustrated in FIG. 3, and allows for creation of the feedback loop 402by coupling the signal output by the power amplifier 102 to the bandpass filter 406. The output signal from the directional coupler 404 isprovided to the band pass filter 406. The illustrated coupler 404 has aninput port 412, a transmit port 414, a coupled port 416, and an isolatedport 418. As shown, the input port 412 is coupled to the output of thepower amplifier 102. The coupler 404 transmits power received from thepower amplifier 102 on the input port 412 to the transmit port 414. Thetransmit port 414 delivers the transmitted power amplifier signal to anantenna switch module or other downstream component. The output powertransmitted to the transmit port 414 can be a reduced version of theinput power amplifier signal received by the coupler 404, where thetransmitted power is reduced by the insertion loss of the coupler 404.The coupler 404 also transmits a portion of the input power amplifiersignal received on the input port 412 to the coupled port 416. Forinstance, the power delivered to the coupled port 416 may be a versionof the input power that is reduced according to a coupling factor of thecoupler 404.

In some embodiments, the band pass filter (BPF) 406 is configured passthrough signals within the protected frequency band (e.g., GPS frequencyband), and to suppress signals that are outside the protected frequencyband. As such, the BPF 406 will pass through the portion of the outputsignal from the power amplifier 102 (e.g., as coupled into the feedbackloop 402 through the directional coupler 404) corresponding to undesirednoise, while suppressing the portion of the output signal thatcorresponds to other frequency bands, including that of the desiredfrequency band (e.g., LTE MB frequencies). As such, the output of theBPF 406 may comprise only the portion of the output signal correspondingto the frequency band of the undesired noise. In some embodiments, theBPF 406 may be implemented as a SAW or a BAW filter. In someembodiments, because it is not directly connected to the output of thepower amplifier 102, the BPF 406 may not need to be able to support highpower handling, unlike the band reject filter 104 illustrated in FIG.1B.

The output of the BPF 406 may be fed back to the input of the poweramplifier 102 as part of a negative feedback loop. In the illustratedembodiment cancellation of the input signal at the input of theamplifier 102 will occur if the loop gain (amplifier gain plusfeedback-path gain) is substantially unity (i.e. 0 dB) and the loopphase (amplifier phase shift plus feedback-path phase shift) issubstantially 180 degrees. In FIG. 4A it is assumed that the blocks arealready designed to accomplish this. In one example, amplifier 102 maybe an inverting amplifier, thus providing the 180 degree phase shift,while coupler 404 and BPF 406 together provide no phase shift and justenough loss to cancel the gain of the amplifier 102. As a result,overall gain from the power amplifier 102 at the protected band isreduced, reducing the output signal strength at the protected frequencyband, and therefore reducing undesired noise in the protected band.

On the other hand, because the BPF 406 does not pass through signalsassociated with frequencies outside the protected frequency band, thefeedback loop 402 will provide minimal or no feedback to the input ofthe power amplifier 102 at those frequencies. As such, for frequenciesoutside the protected frequency band, the gain from the power amplifier102 will remain substantially unaffected by the feedback loop 402.

FIG. 4B is a schematic diagram of a feedback-arranged PA 32 b forsuppressing undesired noise from certain frequency bands (e.g.,protected bands), in accordance with some embodiments, thefeedback-arranged PA 32 b is similar to the feedback-arranged PA 32 aillustrated in FIG. 4A, and further comprises a phase shifter 408 acoupled between the directional coupler 404 and the BPF 406. In someembodiments, the phase shifter 408 a is configured to shift a phase ofthe output signal of the directional coupler 404 (e.g., which couplesthe output of the power amplifier 402 into the feedback loop 402) to beinput to the BPF 406. Phase shifter 408 a is adjusted until the loopphase (amplifier phase shift plus feedback-path phase shift) issubstantially 180 degrees at the undesired frequencies (e.g., thosecorresponding to a GPS or other protected band), resulting in signalcancellation at the undesired frequencies at the amplifier input node.

FIG. 4C is a schematic diagram of a feedback-arranged PA 32 c forsuppressing undesired noise from certain frequency bands (e.g., a GPS orother protected band), in accordance with some embodiments, thefeedback-arranged PA 32 c is similar to the feedback-arranged PA 32 aillustrated in FIG. 4A, and further comprises a phase shifter 408 bcoupled between the output of the BPF 406 and the input of the poweramplifier 102. As such, the phase shifter 408 b may be configured tophase shift an output of the BPF 406 to be fed back to the input of thepower amplifier 102. To maximize the gain of system 32C at the desiredfrequencies, the amplifier 102 should be allowed to operate at thedesired frequencies as if the feedback path were disconnected from itsinput, that is, (1) substantially no feedback signal passes though BPF406, and (2) a very high impedance is presented by BPF 406 to theamplifier input node to avoid loading it down and to avoid creating aleakage path by which some of the desired input signal power would belost. Condition (1) has been discussed previously. Condition (2) isaccomplished by the addition of phase shifter 408 b. The desiredfrequency band will reside somewhere in the stopband of BPF 406, anddepending on the design of BPF 406, the output impedance of BPF 406 inthe desired frequency band may be very high or very low compared to amatched impedance. For example, in a 50 ohm system, the stopbandimpedance of BPF 406 may be a few ohms, or a few hundred ohms. Phaseshifter 408 b is placed between the output of BPF 406 and the input nodeof amplifier 102. Adjustment of phase shifter 408 b effectively rotatesthe output impedance of BPF 406. The adjustment is made such that theimpedance presented to the input node of amplifier 102 is maximized atthe desired frequency band. While one purpose of phase shifter 408 b isto rotate impedance in the desired band as just described, the phaseshifter 408 b also shifts the signal phase of the feedback signal at theundesired frequencies that pass through BPF 406. It is not likely thatone phase shift setting on phase shifter 408 b will simultaneouslyprovide both the maximum impedance in the desired frequency band and thebest signal cancellation in the undesired frequency band.

FIG. 4D is a schematic diagram of a feedback-arranged PA 32 d forsuppressing noise from undesired frequency bands, in accordance withsome embodiments, the feedback-arranged PA 32 d is similar to thefeedback-arranged PA 32 a illustrated in FIG. 4A, and further comprisesboth phase shifters 408 a and 408 b. In some embodiments, the phaseshifter 408 a may shift the signal from the directional coupler 404 by afirst amount, while the phase shifter 408 b may shift the output of theBPF 406 by a second amount. In some embodiments, the phase shifters 408a and 408 b may be configured such that phase shifter 408 b causes BPF406 to present a high impedance to the input node of amplifier 102 inthe desired frequency band. In some embodiments, the phase shifters 408a and 408 b may be configured such that the cascaded phase shifts ofamplifier 102, coupler 404, phase shifter 408 a, BPF 406, and phaseshifter 408 b sum up to 180 degrees in the undesired frequency band. Insome embodiments, the phase shifters 408 a and 408 b may be configuredto satisfy both of these conditions.

In some embodiments, the feedback loop 402 may comprise one or moreadditional components (not shown) configured to change a magnitude ofthe output signal of the directional coupler 404 and/or the BPF 406,thus changing a magnitude of the feedback at the input of the poweramplifier 102.

As described, in the illustrated embodiment the output of the feedbackpath is directly connected to the RF_IN signal, and in suchconfigurations the phase of the output of the feedback path and theRF_IN signal can be 180 degrees or approximately 180 degrees out ofphase, resulting in cancellation of the feedback signal at the input ofthe amplifier 102. This can achieve a simplified design because aseparate component is not used to couple the feedback path to the RF_INsignal. In some other implementations, the cancellation is achievedusing a separate component. For instance, the output of the feedbackpath and the RF_IN signal can be configured as inputs to a 180 degreehybrid coupler, the output of which is connected to the input of theamplifier 102. In such an embodiment, the 180 degree hybrid couplereffectively acts as a summer, which applies a negative sign to one ofthe inputs. To achieve cancellation, the components in thefeedback-arranged PA 32 a would be selected in such an embodiment sothat the output of the feedback path has the same phase or approximatelythe same phase as the RF_IN signal.

FIG. 5 is a graph showing an output signal of a feedback-arranged PA, inaccordance with some embodiments. As illustrated in FIG. 5, the graph 50shows an x-axis corresponding to frequency (measured in GHz), and ay-axis corresponding to signal strength (measured in dB). The graph 500contains a first curve 502 which plots the power gain of thefeedback-arranged PA 32 a over different frequencies.

For example, at most frequencies, such as at points m1 and m2 on thefirst curve 502, (which to frequencies of 1.710 GHz and 1.980 GHzrespectively) the power gain of the feedback-arranged PA 32 a may beapproximately 30 dB. However, near the point m3 corresponding to afrequency of 1.575 GHz, which is within the undesired GPS frequencyband, the gain may be greatly reduced in (˜11.25 dB). Thus, asillustrated in the graph 500, the feedback loop 402 of thefeedback-arranged PA containing the band pass filter 406 may function asa band reject filter, suppressing the signal at the undesired frequencyband.

FIG. 6 is a flowchart of a process 600 for using feedback to suppressnoise in a feedback-arranged PA, in accordance with some embodiments.

At block 602, the feedback loop 402 of a feedback-arranged PA receivesan amplified signal from an output of a power amplifier (e.g., poweramplifier 102), the amplified signal containing an undesired noisecomponent associated with a particular undesired frequency range (e.g.,a GPS noise component). In some embodiments, the amplified signal may bereceived by the feedback loop 402 through the directional coupler 404.

The system can also calibrate the feedback loop 402, before, during, orafter receiving the amplified signal. For instance, the wireless device11 may configure the phase shifter 408 a, phase shifter 408 b, coupler404 and/or band pass filter 406, as applicable, in any of the mannersdescribed herein, such as with respect to FIGS. 4A-4D. For example, theprocessor 20 of the wireless device 11 (FIG. 2), processor 34 of thetransceiver 33 (FIG. 3), or some other appropriate controller or othercomponent of the wireless device 11 can drive one or more control inputsto the phase shifter 408 a, phase shifter 408 b, coupler 404, and/orband pass filter 406, as applicable. As one example, referring to FIG.4D the wireless device can adjust the post-filter phase shifter 408 b toachieve a desired impedance and adjust the pre-filter phase shifter 408a to minimize gain in the un-desired band, as discussed herein.

At block 604, the feedback loop 402 isolates the noise component of thereceived amplified signal (e.g., GPS noise). In some embodiments, thenoise component is isolated using a band pass filter (e.g., BPF 406)configured to pass through the undesired frequency range and suppresssignals outside the undesired frequency range. In some embodiments, thefeedback loop 402 may comprise one or more phase shifters to shift thephase of the received amplified signal or the output of the BPF 406. Insome embodiments, the one or more phase shifters may be configured suchthat the phase of a shifted output of the BPF 406 aligns with a phase ofan input signal of the power amplifier.

At block 606, the feedback loop 402 reduces the gain of the poweramplifier at frequencies corresponding to the noise component. Forexample, in some embodiments, the output of the feedback loop 402 maycorrespond to noise component received from the output of the poweramplifier. By feeding the noise component signal back to the input ofthe power amplifier, overall gain by the power amplifier at theundesired frequency band associated with the noise may be reduced.

As discussed above, use of a bandpass filter and feedback loop may allowfor noise associated with protected frequency bands to be reduced inpower amplifier circuits. In addition, because the bandpass filter islocated along a feedback loop instead of directly receiving the outputof the power amplifier, the required power capacity of the bandpassfilter may be reduced in comparison to if a band rejection filter isused. In some embodiments, an existing commercial bandpass filter may beused to achieve a similar band rejection function as a speciallydesigned band rejection filter. An advantageous feature of thisarrangement is that it can avoid the placement of a notch filter incascade with the PA output, and thereby avoid the passband insertionloss of a such a cascaded filter, which could be 2 dB or more, resultingin loss of as much as 40% of the PA's output power. Here in thisarrangement the only component placed at the PA output is the couplerwhich causes a loss of only about 1% of the PA's output power. Thereforethe entire system can provide much better power efficiency, and can drawless power from its power supply compared to a system with conventionalcascaded notch filter.

Although the illustrated embodiments show a feedback-arranged PA havingone feedback loop 402, in some embodiments multiple feedback loops maybe used. For example, in some embodiments, each of a plurality offeedback loops may contain a BPF configured to pass a differentfrequency band, allowing for the feedback-arranged PA to suppress noiseassociated with multiple different frequency bands.

Some of the embodiments described above have provided examples inconnection with wireless devices or mobile phones. However, theprinciples and advantages of the embodiments can be used for any othersystems or apparatus that have needs for power amplifier circuits.

Such power amplifier circuits can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products, electronic test equipment, etc. Examples of theelectronic devices can also include, but are not limited to, memorychips, memory modules, circuits of optical networks or othercommunication networks, and disk driver circuits. The consumerelectronic products can include, but are not limited to, a mobile phone,a telephone, a television, a computer monitor, a computer, a hand-heldcomputer, a personal digital assistant (PDA), a microwave, arefrigerator, an automobile, a stereo system, a cassette recorder orplayer, a DVD player, a CD player, a VCR, an MP3 player, a radio, acamcorder, a camera, a digital camera, a portable memory chip, a washer,a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A power amplifier system comprising: a poweramplifier configured to receive both a radio frequency signal associatedwith a first frequency band and noise associated with a second frequencyband, to provide amplification to both the radio frequency signalassociated with the first frequency band and the noise associated withthe second frequency band, and to output an amplified radio frequencysignal including the amplified radio frequency signal and the amplifiednoise; and an acoustic wave bandpass filter arranged in a negativefeedback configuration with respect to the power amplifier, the acousticwave bandpass filter configured to pass through the amplified noisecorresponding to the second frequency band to an input of the poweramplifier to provide negative feedback to the power amplifier, resultingin a reduction in an amount of gain from the power amplifier within thesecond frequency band.
 2. The power amplifier system of claim 1 whereinthe first frequency band corresponds to a Long-Term Evolution mid-bandfrequency band.
 3. The power amplifier system of claim 1 wherein theacoustic wave bandpass filter is a surface acoustic wave filter or abulk acoustic wave filter.
 4. The power amplifier system of claim 1wherein the second frequency band corresponds to a global positioningsystem frequency band.
 5. The power amplifier system of claim 1 furthercomprising a directional coupler positioned between an output of thepower amplifier and an input of the acoustic wave bandpass filter. 6.The power amplifier system of claim 1 further comprising at least onephase shifter coupled between an output of the power amplifier and aninput of the acoustic wave bandpass filter.
 7. The power amplifiersystem of claim 1 further comprising at least one phase shifter coupledbetween the output of the acoustic wave bandpass filter and an input ofthe power amplifier.
 8. A wireless device comprising: a transceiverconfigured to generate a radio frequency signal associated with a firstfrequency band; a power amplifier configured to receive both the radiofrequency signal and noise associated with a second frequency band, andto provide amplification to both the radio frequency signal and thenoise, and to output an amplified radio frequency signal including theamplified radio frequency signal and the amplified noise; and anacoustic wave bandpass filter arranged in a feedback configuration withrespect to the power amplifier, the acoustic wave bandpass filterconfigured to pass through the amplified noise corresponding to thesecond frequency band to an input of the power amplifier to providenegative feedback to the power amplifier, resulting in a reduction in anamount of gain from the power amplifier within the second frequencyband.
 9. The wireless device of claim 8 wherein the first frequency bandcorresponds to a Long-Term Evolution mid-band frequency band.
 10. Thewireless device of claim 8 wherein the acoustic wave bandpass filter isa surface acoustic wave filter or a bulk acoustic wave filter.
 11. Thewireless device of claim 8 wherein the second frequency band correspondsto a global positioning system frequency band.
 12. The wireless deviceof claim 8 further comprising a directional coupler positioned betweenan output of the power amplifier and an input of the acoustic wavebandpass filter.
 13. The wireless device of claim 8 further comprisingat least one phase shifter coupled between an output of the poweramplifier and an input of the acoustic wave bandpass filter.
 14. Thewireless device of claim 8 further comprising at least one phase shiftercoupled between the output of the acoustic wave bandpass filter and aninput of the power amplifier.
 15. A radio frequency module comprising: asubstrate; a power amplifier supported by the substrate and configuredto receive both a radio frequency signal associated with a firstfrequency band and noise associated with a second frequency band, toprovide amplification to both the radio frequency signal associated withthe first frequency band and the noise associated with the secondfrequency band, and to output an amplified radio frequency signalincluding the amplified radio frequency signal and the amplified noise;and an acoustic wave bandpass filter arranged in a feedbackconfiguration with respect to the power amplifier, the acoustic wavebandpass filter configured to pass through the amplified noisecorresponding to the second frequency band to an input of the poweramplifier to provide negative feedback to the power amplifier, resultingin a reduction in an amount of gain from the power amplifier within thesecond frequency band.
 16. The radio frequency module of claim 15wherein the first frequency band corresponds to a Long-Term Evolutionmid-band frequency band.
 17. The radio frequency module of claim 15wherein the acoustic wave bandpass filter is a surface acoustic wavefilter or a bulk acoustic wave filter.
 18. The radio frequency module ofclaim 15 wherein the second frequency band corresponds to a globalpositioning system frequency band.
 19. The radio frequency module ofclaim 15 further comprising a directional coupler positioned between anoutput of the power amplifier and an input of the acoustic wave bandpassfilter.
 20. The radio frequency module of claim 15 further comprising atleast one phase shifter coupled between an output of the power amplifierand an input of the acoustic wave bandpass filter.
 21. The radiofrequency module of claim 15 further comprising at least one phaseshifter coupled between the output of the acoustic wave bandpass filterand an input of the power amplifier.